Whilst growing up in the Splott district of Cardiff as a young teenager,
he required operations on his knees, feet and shoulders. Due to the
extent of these operations, a rugby career seemed unlikely.
Sullivan never gave up however, he overcame his early childhood
trauma by being granted a trial by Bradford Northern Rugby League Club at
the age of just 17. Bradford however, passed on the young winger.

Rugby league club Hull, had different ideas about Sullivan and
gave the young man, who boasted phenomenal speed, a chance to play
rugby league. In his debut for Hull, Sullivan had an outstanding
game and gained the support of the Hull club and city. Sullivan
became known for his exceptional speed and the way he would outplay
rugby league's finest opposition wingers. His upper-body was
deceptively strong which gave him excellent cover defence. Despite
his knees which haunted his childhood requiring constant attention
and further operations, he played a total of 352 games for Hull,
scoring 250 tries. In his 213 games
for Hull K.R. he scored 118 tries.

His international career took him to great heights having made
his debut for Great Britain
in 1967. The following year he played three World Cup matches,
grabbing a hat-trick against New Zealand. In 1969, he toured Australasia, but only
participated in one game due to injury. He however won a further
three test caps
against New Zealand
in 1971. In 1972 he was handed the captaincy of Great Britain
and played two tests against France. The World Cup took place that same year,
and he captained Great Britain to become world champions. He scored
a try in each of Great Britain's four games. Sullivan scored
possibly the most famous try in the history of the World Cup to
level 10-10 against Australia in the final, after a length of the
field run.

In 1973 his Great Britain
career came to an end with three tests against Australia. The 1975
World Cup saw Sullivan lead Wales in all four matches, scoring a
try in the defeat of England in the second game for the Welsh team.
Wales ended up finishing 3rd in the five-team World Cup.

When Sullivan died of cancer in 1985 aged just 42,[2]
the city of Hull held him in such high regard
that the main road to the Humber Bridge was named Clive Sullivan
Way.

Sullivan still holds two records for Hull which are: Most tries
in a career (250) and most tries in a match (7) against Doncaster
on 15 April 1968.

Sullivan represented Great Britain
17 times and appeared at three World Cups, 1968 and 1972 with Great Britain
and in 1975 for Wales.